WETTABILITY OF CARBON BY ALUMINUM AND ALUMINUM-ALLOYS

Wetting (both equilibrium contact angle and spreading kinetics) of alu minum and aluminum alloys with silicon and titanium on carbon substrat es is investigated as a function of temperature and carbon microstruct ure. Experiments are carried out by the sessile drop technique under h igh vacuum, in the range from 1023 to 1250 K. Three different types of carbon substrates are examined: vitreous carbon, pyrolytic carbon and graphite pseudo single crystals. It is shown that an increase in temp erature and a decrease in the preferred orientation of the graphite ba sal planes with respect to the substrate surface greatly enhance the t hree-phase line reactivity and the spreading kinetics. From a practica l point of view the results obtained in this study show that in proces ses involving short-time contact (up to a few minutes) between deoxidi zed molten Al (or Al-Si and AI-Ti alloys) and carbon at T < 1273 K, al uminum (or aluminum alloys) does not wet carbon whatever the microstru cture and texture of graphite material. (C) 1998 Elsevier Science S.A. All rights reserved.